(21(4):250-255)柑桔葉片分析在施肥上之應用

The use of leaf analysis as a basis for fertilizer recommendation is now widely practised in the U.S.A., and there appears to be increasing interest in other citrus growing areas of the world. Leaf analysis is used to determine the nutrient status of the tree. It is a valuable aid in obtaining a better understanding of the fertilizer requirements of citrus trees; however, the data obtained as a result of leaf analysis must be used in conjunction with other facts known about the tree. The use of leaf analysis for evaluating the nutritional status of fruit trees assumes that yield, fruit quality, and plant growth are closely related to the concentration of essential minerals in the leaves at the time of sampling. The quantity of an element in the leaves of a plant is a function of several interrelated factors. Among these are leaf age, nutrient supply, moisture conditions, climatic conditions, soil type, crop load, and kind of plant. Leaf analysis integrates the factors that influence the content of nutrients in leaves up to sampling.The physiological basis for leaf analysis rests on the following assumption:ⓐnutrients absorbed from the soil are translocated throughout the plant but are concentrated primarily in the leaves; ⓑthe leaf is a primary site of plant metabolism; ⓒleaf composition indicates change in nutrient supply, and ⓓmaximum yield and satisfactory fruit quality are quantitatively related to range of leaf analysis values when the concentration of an essential element in leaves falls outside the optimum range for a crop like citrus, the addition or omission of that element in the fertilizer should produce a definite responset. Reliable tables of leaf standards must be available for a particular tree crop before leaf analysis results can be properly evaluated.The quickest method of establishing approximate leaf standards is to conduct a survey of commercial planting with good production recordst. Leaf analysis values from these high yielding tree are used in setting up tentative optimum range for the essential mineral elements. Reliable leaf analyses standards become available only after the results of surveys and sand culture experiment are tested against the values obtained from long term fertilizer experiment in the fieldt. Growers depend very heavily on leaf analysis to add minerals. The use of leaf analysis to indicate nutrient availability has long been accepted and its advantages and disadvantages have been recounted. However, its use as a practical tool has awaited the development of standards calibrated with differential treatments on producing tree under field condition; and the growth of commercial laboratories capable of making critical and rapid analyses. In this paper some of the principles of leaf analysis and some of the factors that are particularly important for citrus are briefly discussed. 葉片分析作為柑桔施肥基準的方法，在美國已廣泛應用，因可直接診斷植株之營養狀況，更能瞭解其需肥程度，故在施肥上更為精確，且經濟有效。本文就是柑桔葉片分析中有關採樣技術、樣品之製備、分析方法與各要素之含量標準等問題加以闡述，期能推薦於本省果農應用。 葉片分析受外界因子影響甚鉅，如葉齡、施肥、果實產量、品種、濕度、氣候與土壤狀況等。通常氮素每年分析一次，其他磷、鉀、鈣、鎂約五年分析一次，微量元素則依其葉部徵狀發生後加以分析